Internal combustion engines can utilize a fuel delivery system including a fuel pump for maintaining sufficient fuel pressure. In some conditions, the fuel pump may be operated to control the fuel pressure in response to a fuel pressure sensor located, for example, in a fuel rail or accumulator of the fuel system. In this way, the fuel pressure sensor can provide feedback control to the fuel pump so that the desired fuel delivery may be achieved.
During some conditions, such as in the event of fuel pressure sensor degradation or other degraded operating states, fuel pressure control may be reduced, thereby reducing the accuracy of fuel delivery to the engine. For example, the air/fuel ratio may be richer or leaner than desired potentially causing reduced engine efficiency and/or increased exhaust emissions. In one approach, as set forth in US 2005/0263146, a fuel sensor diagnosis may be performed, wherein the fuel pressure may be estimated based on the air/fuel ratio where an abnormal condition of the fuel pressure sensor occurs.
However, the inventors herein have recognized that other operations may exacerbate the potential error associated with a degraded fuel pressure sensor. For example, if a fuel vapor purging system is operated during conditions where the exhaust gas sensor is used to provide fuel pressure feedback, uncertainties in the amount and/or concentration of the fuel vapors purged to the engine may result in an inaccurate fuel pressure. Likewise, uncertainties in these parameters with adaptive learning of fuel injector characteristics, for example, during conditions where the exhaust sensor is used to provide fuel pressure feedback, may result in inaccurate fuel pressure.
In one approach, the above issues can be addressed by a method of controlling an internal combustion engine having a fuel vapor purging system and a fuel delivery system including a fuel pump and a fuel pressure sensor for detecting the fuel pressure provided by the fuel pump, the method comprising: during a degraded condition of the fuel pressure sensor, adjusting the fuel pump output in response to an operating condition, adjusting at least one of a condition of the fuel vapor purging system and adaptive learning of a characteristic of the fuel delivery system; and further adjusting the fuel pump output in response to an output of an exhaust gas sensor while also adjusting an amount of fuel injected into a cylinder of the engine in response to said output of the exhaust gas sensor.
In this way, by adjusting (e.g., by reducing and/or discontinuing) fuel vapor purging operations and/or adaptive learning during a degraded state of the fuel pressure sensor, fuel pressure control may be improved.
Note however, that alternative embodiments not necessarily related to adjusting fuel vapor purging and/or adaptive learning may also lead to advantageous results.